Belt-tracking construction for belt-type sanding devices and the like



KERING Feb. 25. 1969 J. J. BEC 3,429,078

BELT-TRACKING CONSTRUCTION FOR BELT-TYPE SANDING VICES AND THE LIKE Filed Oct. 27, 1966 Sheet H ill. 4

lll hu J ACOBUS J- BECKERING ATTORNEY Feb. 25, 1969 J. J. BECKERING 3,429,078 BELT-TRACKING CONSTRUCTION FOR BELT-TYPE SANDING DEVICES AND THE LIKE Filed 001;. 27. 1966 Sheet 2 of2 INVENTOR JACOBUS J. BECKERING ATTORNEY United States Patent G 7 Claims ABSTRACT OF THE DISCLOSURE A portable, belt-type sanding device which includes a housing having a motor therein. Drive and idler pulley means are disposed on opposite sides of the motor and have belt means entrained thereover which also is disposed above and below the motor. A novel means is provided to adjust the idler pulley means to insure belttracking and means is provided to tension the belt.

This invention relates generally to power driven pulley devices, and particularly to an improved belt-tracking construction for belt-type sanding devices and the like.

An important object of the present nvention is to provide an improved belt-tracking construction for abrading, burnishing, or polishing devices of the type having driving and idler pulley means and a belt entrained thereover, which construction is simple and compact and therefore minimizes cost and affords use thereof with a relatively large and powerful drive motor while maintaining overall compactness and neat appearance of the device.

Another important object of the present invention is to provide an improved belt-tracking construction of the above character which aifords highly accurate tracking to insure precision in aligning the center of pressure on the idler pulley means with the center of resistance on the belt to maintain the same path of travel for the belt during use.

Still another important object of the present invention is to provide an improved belt-tracking construction of the above character which resists unintended adjustment or tracking during use.

Still another important object of the present invention is to provide an improved belt tracking construction of the above character which is integrated with a belt tensioning construction.

Further objects include the provision of a belt tracking construction of the above character which is relatively inexpensive to manufacture, rugged in construction and reliable in use.

Other objects and advantages of the present invention will become more apparent from a consideration of the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a side elevational view of a typical, compact, belt-type sanding device embodying the present invention;

FIG. 2 is a sectional view illustrating an idler pulley means and belt-tracking construction according to the present invention;

FIG. 3 is an exploded perspective view illustrating the mounting for the belt tracking construction of the present invention;

FIG. 4 is a view, similar to FIG. 3 but reversed in orientation and showing the belt tracking control knob in position in the frame;

FIG. 5 is an enlarged sectional view of FIG. 2 taken along the line 55 thereof;

FIG. 6 is an enlarged side-elevational view illustrating ice the other side of the belt sanding device shown in FIG. 1; and

FIG. 7 is a sectional view of FIG. 2 taken along the line 77 thereof and shown with the idler pulley removed for clarity.

Broadly described, the present invention relates to a belt-type abrading, burnishing or polishing device of the type having a housing, a driving motor, drive and idler pulley means rotatable about generally parallel axes, said drive pulley means being driven by said driving motor, and a belt entrained over said drive and idler pulley means, that improvement which comprises shaft means having a non-rotatable portion and rotatably supporting said idler pulley means and having a longitudinal axis defining a rotational axis of said idler pulley means, bracket means supported relative to said housing for pivotal movement about an axis generally perpendicular to said longitudinal axis, said bracket means being interconnected with said shaft means, and means for moving said shaft means axially whereby to pivot said bracket means on said housing and shift the axis of said shaft, said moving means comprising adjusting means rotatably supported on said housing and threadedly engaging said non-rotatable shaft portion whereby rotation of said adjusting means positively moves said shaft means axially.

Referring now more specifically to the drawings, a typical, compact, belt-sanding device embodying the present invention is illustrated generally at 11 in FIGS. 1 and 6. It should be understood, however, that this illustrated belt sander is by way of example only and that the present invention applies to the general class of belt-type abrading, burnishing and polishing devices.

With this in mind, the sanding device 11 is seen to include a clam-shell housing 12 having upper and lower portions 13, 15. A drive motor (not shown) is supported within a motor housing 14 disposed within the housing 12 and fixed thereto or integral therewith and is adapted to be energized by an electrical power source connected thereto by a conventional line cord (not shown) in the usual manner. Operation of the drive motor is controlled by a trigger switch 17.

An end handle 19 is suitably secured to the housing and is provided with a rear handle grip 21 and a front handle grip 23 for manual control and manipulation of the device 11. The end handle 19 preferably also is of clam-shell construction and houses the trigger switch 17 together with the other electrical control components.

The drive motor is interconnected by a gear transmission (not shown) with a drive pulley 16 journaled within the housing 12 in the usual manner. A removable cover plate 25 is secured to the housing 12 by screws 27 and permits access to the transmission (not shown) for service thereof. The details of the drive motor, the drive pulley and the interconnecting transmission form no part of the present invention and therefore are not illustrated nor described further here. However, for a better understanding of these components, reference may be made to the copending application of Jacobus J. Beckering et 211., Serial No. 610,191 filed J an. 18, 1967, and owned by the assignee of the present invention.

An endless belt 18, suitably formed for abrading, polishing or burnishing operations, is disposed within the housing 12 and is entrained over the drive pulley 16 and an idler pulley 29, and extends above and below the motor housing 14. The belt is tcnsioned over these pulleys so that upon energization of the drive motor, the drive pulley 16 and the idler pulley 29 rotate and the belt 18 travels thereover.

As is customary, the housing 12 is open along one side thereof, as shown at 31 in FIGS. 2 and 6', so that the endless belt 18 can be slipped on and oil? the pulleys.

However, in order for the belt to remain on the pulleys during use, it is necessary for the center of pressure on the pulleys 16, 29 to be aligned with the center of resistance on the belt 18 so as to maintain the same path of travel for the belt. Because of manufacturing tolerances, belt lengths sometimes differ from side to side for each belt and in addition some belt stretching occurs during use. Thus, in order to keep the belt 18 properly centered on the pulleys 16, 29, it is necessary to provide for lateral pulley adjustment so that these length variations are accommodated.

To this end, the idler pulley 29 is, as shown best in FIGS. 2, 6 and 7, rotata-bly supported upon a shaft 33 by axially spaced sleeve or needle bearings 35, 37. The shaft 33 is carried by a generally U-shaped pulley bracket 39 having a pair of arms 41, 43 provided with aligned openings 45, 47 through which the shaft 33 extends. A- base 49 interconnects the arms 41, 43 and is provided with a pair of rearwardly extending parallel legs 51, 53 integral therewith and which slidably receive a pair of forwardly projecting, parallel arms 55, 57 of a support bracket 59. The arm 57 of the support bracket 59 is fixedly secured by screws 61 to a boss 63 integral with the motor housing 14. A pin 65 is pressed in aligned openings 67, 69 in the support bracket legs 51, 53 and is slidably received in aligned slots 71, 73 in the support bracket arms 55, 57 so that the pulley bracket 39 can pivot relative to the support bracket 59 about an axis defined by the pin 65 and can move longitudinally toward and away from the support bracket 59.

As shown in FIG. 2, the shaft 33 is splined at 75 to interferingly engage in the pulley bracket arm opening 45 so that the shaft 33 cannot rotate relative to the pulley bracket 39. A pair of retainer rings 77, 79 hold the idler pulley 29 against axial movement on the shaft 33 rela tive to the pulley bracket 39 and a pair of felt washers 81, 83 are positioned between the retainer ring 77 and the idler pulley 29 and between the pulley bracket arm 43 and the pulley 29, respectively, to reduce friction therebetween.

The end of the shaft 33 extending past the bracket arm 41 is threaded at 85 and is received in a threaded knob 87. The knob 87 has an annular bead 89 rotatably supported in an elongated slot 91 formed at the parting line of the top and bottom housings 13, 15. The outer end of the knob 87 extends outwardly of the housing 12 and is knurled at 93 so that the knob 87 can be turned manually from outside the housing 12.

When the knob 87 is turned in one direction, the threaded, nonrotatable shaft 33 is caused to move axial- 1y away from the knob 87. Since the pulley 29 and the pulley bracket 39 are fixed axially relative to the shaft 33 and since the pulley bracket 39 is pivoted on the support bracket 59 by the pivot pin 65, this axial shaft movement is translated to pivotal movement of the shaft 33, the pulley bracket 39 and the pulley 29 about the axis of the pin 65 in a clockwise direction as seen in FIG. 3. Conversely, if the knob 87 is turned in the other direction, the shaft 33 is moved axially toward the knob 87 and the shaft 33, the pulley bracket 39 and pulley 29 pivot in a counterclockwise direction about the pin 65 as seen in the figure.

In order to accommodate this pivotal movement of the shaft 33, the slot 91 is somewhat longer and wider than the diametral and axial dimension of the head 89 on the knob 87. Thus, when the shaft 33 pivots in a clockwise direction, as seen in FIG. 3, the knob bead 89 swings toward the right-hand end of the slot 91. Conversely, when the shaft "33 pivots in a counterclockwise direction, the bead 89 swings toward the left-hand end of the slot 91.

In order to take up end play in the knob 87, a spring washer 95 is positioned on the shaft 33 adjacent the knob bead 89 and the washer 95 also is trapped in the slot 91. The spring nature of the washer 95 insures a snug fit of the parts in the slot 91 and permits some tilting of the bead 89 in the slot as the bead moves to opposite ends thereof. In addition, the spring biasing effect of the washer on the bead 89 presses the bead frictionally against the side of the slot 91 so as to frictionally hold the knob 87 against unintended turning movement thereof during use of the device. However, to further prevent unintended turning movement of the knob 87, the shaft 33 has an O- ring 97 disposed in an annular groove therein and engaged with a counterbore 99 in the knob 87. This O-ring 97 functions both to frictionally engage the knob 87 and prevent unintended turning movement thereof as well as to prevent the knob 87 from rocking on the shaft 33 during operation of the device 11.

-It will be seen that if the endless belt 18 which is entrained over the pulleys 16, 29 has the same dimensional length from side to side of the belt, the center of pressure on the pulleys will coincide with the center of resistance on the belt if the rotational axes of the pulleys are parallel. Under these conditions, the parts are positioned substantially as shown in FIG. 2. However, if the dimensional length of the belt 18 differs from side to side of the belt, it becomes necessary to adjust the rotational axes of the pulleys 16, 29 in order to align the center of pressure on the pulleys with the center of resistance on the belt 18 and prevent the belt from moving one way or the other laterally of the pulleys. Thus, simply by turning the knob 87, this rotational axis adjustment for the idler pulley 29 is effected as described above.

One of the features of the present invention relates to the fact that the tracking construction described is combined with a belt tensioning construction in a manner adapted to minimize the required space therefor and maximize the space available for the drive motor of the device. Thus, the pulley bracket legs 51, 53 and support bracket arms 55, 57, in addition to being pivotally interconnected as described above, are also longitudinally movable relative to each other by virtue of the pin 65 and slot 71, 73 arrangement. This permits the pulley bracket 39 to move toward and away from the support bracket 59 and the idler pulley 29 toward and away from the drive pulley 16 for belt removal and/ or replacement, and normal belt operation, respectively. The pulley bracket 39 is movable toward and away from the support bracket 59 under the action of an operating lever 101 pivoted on the housing 13 and engageable with a bell crank lever 103 also pivoted on the housing 12. The bell crank lever 103 has a projecting ear 105 engaged in a slotted tab 107 punched out of the bracket base 49. A torsion spring 109 surrounds the pin 65 and has tang portions engaged with the support bracket 59 to normally bias the pulley bracket 39 toward the right as seen in FIG. 2 while pivotal movement of the lever 101 is operable to move the pulley bracket 39 toward the left. A tension spring 111 is hooked to the bell crank lever 103 and the shaft 33 and normally biases the bell crank in a counter clockwise direction and the pulley bracket 39 in a left-hand direction. For a detailed explanation of this construction, reference may be made to the copending application of J acobus J. Beckering et al., Ser. No. 580,367, filed Sept. 19,1966, now Patent No. 3,393,573 and owned by the assignee of the present application.

It will be appreciated that by providing the tracking construction directly on the pulley shaft 33, a minimum of structure is needed and this together with the fact that this construction is integrated with the belt tensioning construction leaves a maximum of space available for the drive motor of the device. Thus a larger, more powerful drive motor can be employed without making the overall device bulky and cumbersome to handle and manipulate. Furthermore, the threaded relation between the shaft 33 and the knob 87, together with the trapped relation of the knob bead 89 and the spring 95 provides for close and accurate adjustment of the idler pulley 29.

By the foregoing, there has been disclosed an improved belt-tracking construction for belt-type sanding devices and the like calculated to fulfill the inventive objects hereinabove set forth, and while a preferred embodiment of the present invention has been illustrated and described in detail, various additions, substitutions, modifications and omissions may be made thereto without departing from the spirit of the invention as encompassed by the appended claims.

I claim:

1. In a belt-type abrading, burnishing or polishing device of the type having a housing, a driving motor, drive and idler pulley means rotatable about generally parallel axes, said drive pulley means being driven by said driving motor, and belt entrained over said drive and idler pulley means, that improvement which comprises shaft means having a non-rotatable portion and rotatably supporting said idler pulley means and having a longitudinal axis defining a rotational axis of said idler pulley means, bracket means supported relative to said housing for pivotal movement about an aXis generally perpendicular to said longitudinal axis, said bracket means being interconnected with said shaft means, and means for moving said shaft means axially whereby to pivot said bracket means on said housing and shift the axis of said shaft, said moving means comprising adjusting means rotatably supported on said housing and threadedly engaging said non-rotatable shaft portion whereby rotation of said adjusting means positively moves said shaft means axially.

2. A construction as defined in claim 1 wherein said adjusting means has a bore threadedly receiving one end of said shaft means.

3. A construction as defined in claim 1, wherein one of said adjusting means and shaft means is provided with an annular bead rotatably supported in a slot in said housing, said slot being elongated to allow lateral movement of said adjusting means with pivotal movement of said bracket means.

4. A construction as defined in claim 3 wherein said adjusting means threadedly receives said shaft means and said bead is provided on said adjusting means, and which includes a spring washer on said shaft means and engaging said annular bead, said spring washer being positioned in said slot to take up slack between said annular bead and said slot.

5. A- construction as defined in claim 2 which includes an annular ring of friction material interposed between and engaging said shaft means and said adjusting means to prevent inadvertent turning movement of said adjusting means.

6. A construction as defined in claim 3 wherein said housing includes detachably secured frame members, said slot being formed at the parting line between said frame members.

7. A construction as defined in claim 1 wherein said bracket means is supported upon said housing for m0vement in a direction generally perpendicular to said longitudinal axis.

References Cited UNITED STATES PATENTS 2,272,273 2/1942 Parker 5l--170 2,686,392 8/1954 Moore 51-170 2,893,176 7/1959 Bruck 51--170 3,176,436 4/1965 Anton 51170 3,267,619 8/1966 Herder 51l48 LESTER M. SWINGLE, Primary Examiner.

D. G. KELLY, Assistant Examiner.

U.S. Cl. X.R. 5 l 

